Sweep circuit



y 15, 1 2 J. M. LESTER ET AL 2,603,747

SWEEP CIRCUIT Filed April 24, 1944 29 AMPLIFIER AND OSCILLOSCOPE INVERTER l FIG 2.

i VGIZ 35 B V 34 I INVENTOR J. M. LESTER %R%ILK RSON And EY Patented July 15, 1952 SWEEP CIRCUIT:

J ohnk M. Lester, Rockville Centre, and, Jeflerson R.Wilkerson,gBayside, N, Y.,. assignors to The Sperry Corporation, a corporation-of Delaware Application April 24', 1944;.Serial No; 532,502

Claims. (Cl. 25 1-27):

This invention relates to electronic circuits generally. and is particularly concerned with.

sweep voltage generating apparatus for oscilloscopes.--

The principal object of the presentinvention iaitoprovidea circuit which will produce a substantially' linear sweep- .voltageof short dura-, tionirom a square voltage wave with. a minimum number of circuit elements. Otherobjects and advantages of the invention will become apparent as the description proceeds. v

vIn its preferred form, the invention provides aspluralityv of electronic discharge devices which are connected to control the charging and dischar'gingoi a capacitive element for the generation-of a sweep voltage. One of thedischarge devices operates to effect the chargingv of the capacitive element and to institute its discharge; The second device is connected to interrupt the discharge of the capacitiveelement at. a time whenqtherate of discharge is still esssentially linear, and this linear portion of the exponential discharge of the capacitive element is taken from across the-element as thedesi-red sweep voltage. A morecomprehensiveunderstanding: of the invention willbe afforded from the following detailed description when considered in connection with the accompanying drawing, in which Fig; 1 -is a schematic circuit diagram of an embodiment of the invention; and I Flg.-2 isa graph; of various electrode voltages and currents developed within the :circuit illustrated in Fig. 1. r H

the'form illustrated in Fig. 1, theinvention provides an electronicdischa-rge device II,- having-dualelements I2 and I3, each of which'may be considered as a single triode. Grid I l-oi element I2 is connected toreceive a square wave non-conducting, condenser I8 discharges through resistor 2|. The discharge from condenser I8 drives cathode 20 of element I3 more negatively with respect to its grid until thiseIement becomes conducting, thus preventing condenser I8 from discharging any further; Condenser, I8 remains at this voltage level untiltime t: when the square input, wave again drives grid" IB' of element I2 positively and thecycle is repeated. In this manner, the discharge is interrupted at a time when it is taking place at a substantially linear rate,. andthis portion of theoutput of capacitive element I8 isdelivered to the output terminalsv 28 as. thesweep voltage, the slopeoi which is controlled by the time constant of the R. C, network. and. I8. The amplitude of thevsweepris determined by the selection of the biasing elements 26 and 21 which determine the amount ofibiasapplied togrid 25 of element I3 and thereby control. the level at. which element I3 becomes conductingto interruptithe discharge of capacitive element I8.

The operation of. the circuit may be more clearly visualized withthe aid of Fig. 2. 'in' which from-input terminal lithrough long time constant grid-leak coupling elements comprising a capacitor I6-and a resistor H. A capacitive element I8 is connected in the lead of cathode I9 "of element I2, which has in parallel therewith a resistor 2|. Both of the anode electrodes 22 and 23 receive 'positive'energy from source 24 and bias is supplied to grid 25 of element I3 by means of a voltage divider consisting of the resistors 26 and 21. The output-of the'circuit istaken across the capacitance I8 and delivered to output terminals 28, or may be delivered to an amplifying and inverter device 29 from which itis delivered to the deflecting zelements'of'an oscilloscope. When the square wave 32 reaches grid I4 and: at time h, thegrid I4 is driven positive and condenser I6 is charged to a-negative value with respect to cathode I9. At time 252 the grid is driven negatively-and element I2 is cut off. During the time interval t1t2; condenser I8 has been charged and when element I2 becomes the wave form A represents the grid voltage of element I2, B the cathode voltage of both elements I2 and I3, and C and D, the respective currents, of elementsv I2 and, I3. At time t; (Fig. 1),. the grid voltage of the element I2 is seen to be less than the 28+ level of source 14 and remains ,so duringvthe time when the ele-' ment. is conducting, andalso when capacitive element I8 is being charged. At time t2, the

tube. iscutoif andthe grid volta e .is seen to fall Simultaneously, capacitive element I8 starts to discharge through the resistive element 2| and the cathodes 0f bothjelements are" seen to decrease as illustrated at1B between-point 35 and point .34. The cathode voltage continues I to decrease to the point Monthe exponential curve 33 at which point. the potential difference between cathode 2 0 of element I3 and grid25 becomes insuficient to. retain element I3 nonconducting, and hence element I3 passes current; maintaining condenser I8 c'harged'to potential V That portion of 'the discharge voltage wave lyingbetween the points '34 and 35 on curve 33 accomplishes the range sweep action desired] in oscilloscopefll. r

With reference to current curves. C and'D; it will be noted that .current tovelement I2 falls airtime t2, whereasielement I3 remains nonconducting until its cathode reaches a. certain potential level (V under .'the influence, ofuthe discharge of capacitive element Ill 3 to render the tubeconducting, whereupon the current. rises as shown in Fig. 2D:

As previously stated, the slope of the. sweep output wave portion 35--34 is determined .by the qtimei constant 1 B21618. The 'output:- sweep less of the input amplitude if a fair degree of f linearity is to be assured.

Since many changes could be inade 'inthe.

above construction and many apparently widely difierent embodiments of this invention could be made without departing from, the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and notina limiting sense. I 'Whatis claimed'is: 1 I

, .1. In a sweep voltage generator circuit, a capacitive element; first and second electron dischargedevices each having a cathode, a-control electrode and an anode, the cathodes of said first and second devices being connected to said ca-j pacit'ivel element; an anode potential source connected in series with said capacitive element between the anodes and the cathodes of said first and second devices for'polarizing said anodes positively'with respect to. said cathodes; circuit means connected to said first device recurrently Yaryingthe control electrode potential thereof between two predetermined values producing re-, current variations .of current through said first device from said sourceffor recurrently charging saidj capacitive element to' a first voltage value; andmeans. for maintaining'the control electrode of said second device at a predetermined potential positive relative to the junction of said capacitive element and said source but negative withrespect to said cathodes for determining a second voltage of said capacitive element at which said second device passes'a charge-sustaining current from said source.

, 2. Sweep voltage generating apparatus comprising first and second electronic discharge devices, each having plate, grid, and cathode electrodes, input terminal means for applying a square-wave voltage on the grid electrode of said .fir'st device through grid-leak coupling means,

a capacitive element. connected in the cathode leadofl said first device having a resistance in parallel therewith, means for interconnecting the cathode leads of both devices, positive energy supply means for the plateelectrodesof both devices, means for supplying a positive biasing voltage to the grid. electrode of said second device relative to the terminal of said capacitive element opposite its terminal connected to the cathodes of said devices, and output terminal means connected across said capacitive element.

- 3. In combination, a first electron discharge device having a cathode, an anode anda control grid, a resistor'and a capacitor connected in parallel, one junction of the parallel resistorcapacitor combination being connected to the cathode of said first device, power supply means for maintaining the anode of said electron discharge device biased positively with respect to its cathode, said power supply means comprising a voltage source having a negative terminal connected to the junction of said resistor and capacitor opposite from said cathode, means coupled to the grid of said first device for alternately rendering it conductive to charge said capacitor to a first voltage and rendering it nonconductive to permit discharge of saidcapacitor, and means including a second electron discharge device for arresting the discharge 01' said capacitor at apredetermined second voltage lower than said first voltage, saidsecond electron discharge device having, a cathode, a control grid and an anode, and said last named means including means for maintaining the anode of said second device positive with respect to its cathode, means connecting its cathode in series with said capacitor, and means for maintaining its control grid at a predetermined positive voltage with respect to the junction between said power supply means and said capacitor and resistor less than said first voltage.

4. A sweep voltage generator circuit compris ing first and second electron discharge devices each having a cathode, an anode and a control electrode, a capacitor and resistor in shunt connected at one junction to the cathodes of said devices, anode voltage supply means connected between the junction of said capacitor and resistor opposite said cathodes and the anodes of saiddevices for polarizing their anodes positively with respect to their cathodes, means for biasing the control electrode of said second electron discharge device to a fixed potential intermediate between the potential of the anode of said second discharge device and the negative potential of said'supply means, and means supplying high-amplitude square waves between the control electrode and the cathode of said first electron discharge device for rendering said first device alternately conductive and non-conductive.

5. In combination, a pair of electron discharge devices each having an anode, a cathode and a control grid, means connecting the anodes of said devices in parallel and the cathodes of said devices in parallel, a shunt circuit of a resistor and a capacitor, a first junction of said shunt circuit being connected to said cathodes, means for maintaining said anodes at a positive potential above the cathodes, said means including a voltage source connected between the other junction of said shuntcombination and said anodes means' coupled to thegrid of said first tube for rendering'it alternately conductive and non-conductive, said capacitor being charged during the periods of conductivity, and means maintaining thegridof said'second device at a predetermined positive potential withrespect to the junction of said voltage source and said shunt resistor-capacitor circuit. 1

JOHN M. LESTER. JEFFERSON R. W'ILKERSON.

file of this .patent:

UNITED STATES PA'I'ENTS Number Name Date 2,113,220 Power Apr. 5, 1938 2,209,436 White July 30, 1940 2,210,523 Blumlein Aug. 6, 1940 2,241,256 Gould May 6, 1941 2,241,619 Sherman May 13, 1941 2,248,975 Faudell July 15, 1941' 2,265,848 Lewis Dec. 9, 1941 2,300,189 1 Wolfi Oct. 27, 1942 2,300,632 Poch l Nov. 3, 1942 2,345,668 Hallmark Apr. 4, 1944 2,347,008 Vance Apr. 18, 1944 2,350,069 Schrader et al May 30, 1944 2,355,363 Christaldi Aug. 8, 1944 

